Faculty Bibliography

Microwave energy is a relatively new energy modality that is being used for surgical atrial ablation as a treatment of atrial fibrillation. Microwave energy works by dielectric heating and has a favorable thermal profile that permits both rapid endocardial and epicardial ablation. The device is also extremely flexible and can be easily adapted to minimally invasive applications. The device has been used in over 600 patients with a success ranging from 70% to 90% and without any device-related complications. Many of these patients have had their ablations performed from the epicardium on the beating heart without the aid of cardiopulmonary bypass. Microwave atrial ablation is likely to become an important part of the surgical armamentarium, particularly for those performing minimally invasive approaches to cure atrial fibrillation.

The purpose of this article is to present and evaluate the various technologies recently developed for the surgical treatment of atrial fibrillation as alternatives or adjuncts to the traditional Maze III procedure and other "cut and sew" techniques. The discussion contains a detailed consideration of the biophysical background of the most common ablation techniques, their mode of tissue injury, the methods of use, and the related complications through a review of the existing literature and analysis of experimental results. All of the current technologies presented are still being tested to augment the success rates and reduce the incidence of complications, although all are not available for clinical use. Radiofrequency and cryoablation have been used clinically on large numbers of patients with varying results. Microwave technology has been used in small groups of patients, and the results are to be evaluated. Laser technology is still in an experimental phase, and the clinical results are forthcoming. True transmurality, reduction of operative time, friendly use of ablation devices, and substantial reduction of complications appear to be the key factors for broad adoption of alternative energy sources for surgical ablation.

BACKGROUND: Patients with prolonged intensive care unit (ICU) stays after cardiac operations are labor intensive and expensive. We sought to determine whether exhaustive ICU efforts result in survival or quality-of-life benefits and whether outcome could be predicted. METHODS: We retrospectively analyzed all adult cardiac surgical patients in 1998 for ICU stays more than 14 days. Data were analyzed to create multiple organ dysfunction scores (MODS, range 0 to 24) and hospital charges. Follow-up was conducted 1 and 2 years apart for survival and quality-of-life evaluation. RESULTS: Forty-nine patients remained in the ICU more than 14 days, comprising 3.8% of our patients but 28% of total ICU bed time. This population had a 28.5% hospital mortality, which was greater than those in the ICU less than 14 days (5.3%, p < 0.05). By 2 years, 22 of the 35 discharged patients were alive, 16 of whom had a normal quality of life. Patients alive at 2 years had lower MODS at day 14 than those who died (2.6 +/- 1.4 versus 5.5 +/- 3.8; p < 0.005) as well as lower hospital costs ($223,000 +/- $128,000 versus $306,000 +/- $128,000; p < 0.05). No patient with an MODS of at least 6 at day 14 survived. CONCLUSIONS: Patients remaining in the ICU for more than 14 days suffer a higher mortality at greater expense. A MODS at day 14 may help predict those who will not enjoy long-term survival and thus aid in the decision to terminate care.

Epicardial direct cardiac compression for cardiogenic shock avoids a blood surface interface with associated thromboembolic and immunologic sequelae and could be placed rapidly with technical ease. The Cardio Technologies device provides synchronized biventricular cardiac compression, is placed via a thoracotomy, and remains on the heart without need for sutures. In preclinical work, the system has successfully restored cardiac function to near normal in the setting of heart failure. The CardioSupport system offers an attractive and novel alternative for treating cardiogenic shock and is being prepared for upcoming clinical trials.

BACKGROUND: Preformed anti-human leukocyte antigen (HLA) antibodies delay heart transplantation in patients with left ventricular assist devices (LVAD) because of difficulty in finding crossmatch-negative donors. These antibodies may also be associated with adverse outcome after transplantation. METHODS: In a retrospective analysis of 40 patients with LVAD at Columbia-Presbyterian Medical Center between 1990 to 1996, age, sex, diagnosis, race, duration of support, transfusions, and infections were studied by univariate and multivariate analysis as predictors for development of either anti-HLA class I (anti-I) or anti-HLA class II (anti-II) immunoglobulin G (IgG) or M (IgM) antibodies. RESULTS: Eighteen (45%) patients had development of anti-I and 20 (50%) had development of anti-II antibodies over the study period. Median time for LVAD support was 142 days (range 35 to 439). Only total number of perioperative platelet transfusions predicted the development of anti-I IgG antibodies (p = .04). No other associations were found for development of anti-I IgM or anti-II antibodies of either IgG or IgM specificity. Patients who had development of anti-I IgG received a mean of 13.9 (SE +/- 2.6) units of platelets compared with a mean of 7.7 (SE +/- 2.3) units in those who did not (p = .01). By Kaplan-Meier analysis, at the median duration of follow-up, 8% of patients receiving < 6 units were predicted to have development of anti-I antibodies compared with 63% receiving > 6 units (p = .002). In the last 7 patients, leukocyte filters were used to decrease the antigenic load during platelet and red blood cell transfusions. Only 1 of 7 (14%) patients had development of anti-HLA antibodies compared with 31 of 33 (94%) in whom filters were not used (p < .005). CONCLUSIONS: These results indicate that platelet transfusion during LVAD implantation is a risk factor associated with development of HLA class I IgG antibodies. Use of leukocyte filters during platelet transfusion may decrease the risk of development of anti-HLA antibodies.

Biologic grafts are the conduit of choice for vascular reconstructive procedures. The short-term thrombogenicity, patency, and stability of bovine arterial grafts, altered by a dye-mediated photo-oxidation process, was evaluated in the canine common femoral vein (CFV) and artery (CFA) model. Modified bovine interposition grafts were implanted in the CFV of 12 dogs and in the CFA of 11 dogs, respectively. Polytetrafluoroethylene (PTFE) implants on the contralateral side served as controls. Patency and histology were assessed at 1, 2, 4, and 6 weeks. In the CFV, patency of photo-oxidized grafts was 83% at 1 week and 71% at 2 weeks, compared to 17% and 0% for PTFE, respectively (p = 0.0033). In CFA, patency was 82% for the photo-oxidized graft and 63% for PTFE at 6 weeks (p = NS). Photo-oxidized grafts were nonreactive, without evidence of degenerative changes or cellular infiltration at all time periods. Compared to commercially available PTFE, photo-oxidized arterial grafts have superior patency in the CFV, and comparable patency in the CFA. Preliminary results demonstrate that these xenografts are stable and without degenerative changes. If corroborated by long-term data, these grafts may be a suitable alternative to currently available prosthetics for peripheral vascular reconstructive procedures.

BACKGROUND. An alternative to mechanical stapling or hand suturing is needed to permit laparoscopic common bile duct exploration. We evaluated the strength and healing characteristics of canine choledochotomies sealed with a fibrinogen solder and a diode laser. METHODS. After creation of a 0.5 cm longitudinal choledochotomy, the edges were coapted with forceps, and a fibrinogen solder mixed with indocyanine green dye was applied. The solder was sealed in place with an 810 nm diode laser (125 W/cm2). RESULTS. Immediate mean leakage pressure was 264 +/- 7 mm Hg compared with 83 +/- 66 mm Hg in suture controls. This increased to 364 +/- 115 mm Hg at 2 days and was more than 510 mm Hg at 7 days. On histologic examination rapid reabsorption of the solder with no signs of inflammation or stenosis was seen. No episodes of dehiscence or peritonitis occurred. CONCLUSIONS. Laser soldering provides a watertight choledochotomy closure with adequate immediate strength allowing a reliable, technically feasible common bile duct exploration via a laparoscopic approach

Despite success with autologous tissue welding, laser welding of synthetic vascular prostheses has not been possible. The graft material appears inert and fails to allow the collagen breakdown and electrostatic bonding that results in tissue welding. To develop a laser welding system for graft material, we repaired glutaraldehyde-tanned human umbilical cord vein graft incisions using laser-assisted fibrinogen bonding (LAFB) technology. Modified umbilical vein graft was incised transversely (1.2 cm). Incisions were repaired using sutures, laser energy alone, or LAFB. For LAFB, indocyanine green dye was mixed with human fibrinogen and the compound applied with forceps onto the weld site prior to exposure to 808 nm diode laser energy (power density 4.8 W/cm 2). Bursting pressures for sutured repairs (126.6 +/- 23.4 mm Hg) were similar to LAFB anastomoses (111.6 +/- 55.0 mm Hg). No evidence of collateral thermal injury to the graft material was noted. In vivo evaluation of umbilical graft bonding with canine arteries demonstrates that LAFB can reliably reinforce sutured anastomoses. The described system for bonding graft material with laser exposed fibrinogen may allow creation or reinforcement of vascular anastomoses in procedures where use of autologous tissue is not feasible

A simple and inexpensive means of creating autologous fibrin glue is described that avoids the potential disadvantages of conventionally obtained material. This improvement may allow more widespread use of fibrin glue for operative bleeding